There is conventionally known an illumination device for irradiating light coming from an LED unit in a specified direction through a reflector having a curvilinear reflection surface (see, e.g., Japanese Patent Application Publication No. 2008-226788 (JP2008-226788A), FIG. 2)
Referring to FIG. 15, the illumination device 100 disclosed in JP2008-226788A is used as a vehicle lamp unit and includes an LED package 101 as a light source and a reflector 102. The illumination device 100 is built in a front end portion of a motor vehicle and is used as a reflection-type lamp unit for emitting irradiation light along an optical axis AX.
The LED package 101 includes an LED chip 101A and a substrate 101B for supporting the LED chip 101A. The substrate 101B is attached parallel to the optical axis AX. This means that the major optical axis of the LED package 101 is orthogonal to the optical axis AX.
The reflector 102 has a revolution-paraboloid-type reflection surface 103 whose center axis coincides with the optical axis AX and whose focal point lies on the light-emitting center of the LED package 101, namely on the LED chip 101A. A direct light control member 104 for interrupting the direct light coming from the LED package 101 is arranged at the front side of the irradiation direction near the LED package 101.
The LED package 101, the reflector 102 and the direct light control member 104 are attached to a generally L-shaped metal bracket 105. The metal bracket 105 includes a vertical wall 106 and heat-dissipating fins 107 formed at the rear side of the vertical wall 106.
Therefore, the light emitted from the LED package 101 is reflected by the reflection surface 103 and irradiated as parallel light traveling along the optical axis AX. At this time, the direct light is interrupted by the direct light control member 104. Thus, no direct light is irradiated on a specified area.
When replacing the LED package 101, it is necessary to remove the reflector 102 in usual cases. Since the illumination device 100 disclosed in JP2008-226788A is used as a single body, the reflector 102 is first removed to perform replacement of the LED package. Thereafter, the reflector 102 is attached again.
In case of an illumination device provided with a plurality of LED packages and a plurality of reflectors, it is sometimes the case that the orientations of the respective reflectors are finely adjusted to change the area to be irradiated. In this case, the task of individually removing each of the reflectors to replace one of the LED packages is troublesome. Another problem resides in that the fine adjustment performed after attachment of the reflector is cumbersome and may impair the ease of work.
In an illumination device that makes use of LEDs, the heat radiation performance thereof needs to be improved because an increased amount of heat is generated along with an increase in the output power of the LEDs. In particular, there is a problem in that heat radiation is hard to perform in a sealed device.
Turning back to the illumination device 100 disclosed in JP2008-226788A, the substrate 101B for supporting the LED chip 101A is attached parallel to the optical axis AX. Therefore, the major optical axis of the LED package 101 is orthogonal to the optical axis AX. This reduces the effective reflection area on the curvilinear reflection surface and leads to insufficient reflection efficiency. From the standpoint of energy saving, it is required to improve the reflection efficiency.